The invention relates to the manufacture of superconducting members.
By superconducting member is meant a member which will exhibit superconductivity when its temperature is lowered below its critical temperature. Materials of particular interest in this field are those which have comparatively high critical temperatures and comparatively high critical magnetic fields. Such materials are compounds of the A15 crystal structure having the general formula A.sub.3 B where A comprises niobium or vanadium and B typically comprises one or more of the elements aluminium, gallium, indium, silicon, germanium and tin.
The invention is more particularly concerned with the manufacture of a superconducting member comprising a large number of fine superconductive filaments supported in an electrically conductive, non-superconductive matrix, and is an improvement in or development of the inventions described in U.S. Pat. No. 3,728,165 and application Ser. No. 584,905 filed June 9, 1975 as a continuation of application Ser. No. 383,476 filed July 30, 1973.
A.sub.3 B compounds with A15 crystal structure are sometimes superconducting with high temperatures of transition from the superconducting to the normal state. These compounds cannot be produced as multifilamentary superconductors by techniques suitable for ductile superconductors because they are very hard and brittle materials. One method suitable for producing A.sub.3 B compounds as multifilamentary superconductors is described in U.S. Pat. No. 3,728,165. For example, rods or wires of the element A are embedded in a matrix of a carrier metal containing the element B. Copper is a suitable carrier metal for the production of Nb.sub.3 Sn or V.sub.3 Ga by this method and the alloy of the carrier metal with the element B is conveniently referred to as "the bronze" or "the Cu--B alloy". The B element is generally in solid solution in the carrier metal since this provides a ductile alloy, but the method can also work when the B element is also present in other phases in the bronze. The element A and the Cu-B alloy may both contain additions of other elements. The composite of rods of element A in a matrix of bronze is fabricated by a simple mechanical deformation process to produce fine filaments of element A in the required configuration in the bronze matrix. The filaments of element A are then converted to compound A.sub. 3 B by reaction with the B element from the bronze by heating in a temperature range in which the bronze in contact with the element A remains in the solid state.
It is noted in U.S. Pat. No. 3,728,165 that the alloy (Cu-B alloy) may contain other elements in the form of acceptable impurities or additives or diluents which do not unacceptably affect the reaction between the niobium or vanadium with the B element to form the superconducting compound.